After almost five years in jail, he wrote two books and started an IT consulting firm

He can find former President George Bush”s Social Security number and Leonardo DiCaprio”s mother”s maiden name in under 15 seconds, and led the FBI on a three-year manhunt as he hacked his way into the world”s biggest firms. Computer terrorist” Kevin Mitnick is one of the world”s most famous computer hackers and became a cause celebre after breaking into networks and stealing software at companies including Sun Microsystems and Motorola.

Now Mitnick, a U.S. citizen, travels the world teaching companies how to guard against people like him.He argues that while sophisticated technology can help keep networks clean from viruses, it is useless if hackers can con a company”s employees into handing over passwords by posing, for example, as colleagues.

“Hackers find the hole in the human firewall,” Mitnick told an IT security conference yesterday in Johannesburg, South Africa. “What”s the biggest hole? It”s the illusion of invulnerability.”